[lldb][NFC] Refactor printing of short options in help

[lldb][NFC] Refactor printing of short options in help

Instead of building a set twice for optional and required,
build a set for each while walking the options once.

Then take advantage of set being sorted meaning we don't
have to enforce the upper/lower order ourselves.

Just cleaned up the formatting on the later loops.
Combined the if conditions and used a single line if.

Depends on D123501

Reviewed By: jingham

Differential Revision: https://reviews.llvm.org/D123502